We have used homologous recombination in human embryonic stem cells (hESCs) to insert sequences encoding green fluorescent protein (GFP) into the NKX2

Hypoxia inducible pathway markers continue to be over expressed in sarcomatoid clear cell renal cell carcinoma, and can be of diagnostic usefulness in such high grade tumors. Over expression of vascular endothelial growth factor in the clear and nonclear cell groups raises the possibility that vascular endothelial growth factor targeted therapies may have a role in the management of sarcomatoid renal cell carcinoma, and deserve further investigation.

Multiple therapeutic options for renal tumors that are now available have put pathologists under increasing pressure to render diagnosis on limited material. Results on biopsies by hematoxylin and eosin (H&E) have historically not been encouraging. Currently, multiple immunohistochemical markers with differential expression in these renal tumors are available. We studied the utility of such markers on needle biopsies that were obtained ex vivo. After nephrectomy, two 18-guage cores were obtained and processed routinely. Expressions of carbonic anhydrase (CA) IX, CD117, α-methylacyl-CoA racemase (AMACR), cytokeratin 7 (CK7), and CD10 were evaluated. Results, with or without immunostaining, were compared with the final nephrectomy diagnosis. We studied 145 tumors, including 119 renal cell carcinomas (83 clear cell, 18 papillary, 14 chromophobe, and 4 type unclassified), 11 oncocytomas, and 15 miscellaneous tumors. Adequate evaluable material was present in 123 (85%) cases. In such biopsies, 81% of cases were correctly classified by H&E alone, with correct diagnosis in 90% of cases in the most common tumor subtypes (clear cell, papillary and chromophobe renal cell carcinoma, and oncocytoma). By adding immunostains, the accuracy was 90% overall and 99% among the 4 most common subtypes. The following extent and patterns of immuneexpression were highly useful in the diagnoses: diffuse, membranous CAIX expression in clear cell renal cell carcinoma, diffuse positivity for AMACR in papillary renal cell carcinoma, distinct peripheral cytoplasmic accentuation for CD117 in chromophobe renal cell carcinoma, widespread and intense positivity for CK7 in chromophobe and papillary renal cell carcinoma, and diffuse membranous reactivity in clear cell and patchy/luminal in papillary renal cell carcinoma for CD10. In conclusion, utilizing immunostains improves classification of renal tumors on needle biopsy, which may be of particular help for pathologists with limited experience. Both extent and patterns must be considered for a definitive diagnosis.

Carbonic anhydrase IX (CAIX)-a protein maintaining intracellular and extracellular pH-reportedly also influences regulation of cell proliferation, oncogenesis, and tumor progression. Its expression is von Hippel-Lindau-hypoxia inducible factor pathway dependent. Immunohistochemical (IHC) studies show that CAIX is diffusely overexpressed in clear cell renal cell carcinoma (CRCC), making it a potentially important differential diagnostic marker. Prognostically, low CAIX expression reportedly indicates poor survival and low response to interleukin therapy in CRCC. Most IHC studies have used clone M75 as the primary antibody, which is not commercially available. We evaluated a new commercially available antibody (clone NB100-417) to assess its expression in CRCC and compared its results with M75. On a tissue microarray of CRCC, IHC staining was performed using both antibodies. The immunoreactivity was graded as 0; 1+, 1% to 25%; 2+, 26% to 50%; and 3+, >50% tumor cells immunoreactive. Ninety-one out of ninety-five (96%) cases showed similar staining grade with excellent agreement (kappa=0.65, weighted kappa=0.75). Grade 3+ expression of CAIX was observed in 89 (94%) cases each, with both antibodies. Both antibodies produced intense membrane-predominant expression, limited to tumor cells. More than 95% of the tumors with low nuclear grade, compared with 84% and 88% of tumors with high nuclear grade, showed 3+ expression using both antibodies. Thus, most CRCC show strong and diffuse expression of CAIX, and the expression is comparable using both antibodies. Therefore, similar to the clone M75, NB100-417 can be used as a diagnostic and potentially a prognostic marker in CRCC, with the advantage of its commercial availability.